Direct positive fogged silver halide emulsion sensitized with a cyclo-heptatriene cyanine dye

ABSTRACT

5-(O=)CYCLOPENT-1-ENE   1-((-Z2-N(+)(-R)=(CH-CH)M=)&gt;C-L2-L1-),2,3-(-Z-),4-Z1,   A DIRECT POSITIVE SILVER HALIDE EMULSION COMPRISING AT LEAST ONE DYE OF THE FORMULA: WHEREIN Z IS AN ORGANIC SUBSTITUTED OR UNSUBSTITUTED ATOMIC GROUP NECESSARY TO COMPLETE A CYCLOHEPTATRIENE RING, WHICH MAY BE OPTIONALLY SUBSTITUTED WITH A TROPONOID COMPOUND; Z1 IS AN OXYGEN ATOM OR N-H; ZI IS AN ORGANIC SUBSTITUTED OR UNSUBSTITUTED ATOMIC GROUP NECESSARY TO COMPLETE A 5 OR 6 MEMBERED HETEROCYCLIC RING; R IS A MEMBER OF THE ALKYL SERIES SELECTED FROM THE GROUP CONSISTING OF LOWER ALKYL, HYDROXY (LOWER) ALKYL, LOWER ALKOXY, SULFO (LOWER) ALKOXY, VINYL, METHYL ARALKYL AND SULFO ARALKYL; L1 AND L2 ARE A GROUP FROM THE METHINE SERIES, SAID L2 CAPABLE OF FORMING A METHYLENE CHAIN TOGETHER WITH SAID R; X IS AN ANION, AND M AND N EACH IS 0 OR 1, PROVIDING THAT N IS 0 WHEN THE DYE FORMS AN INTRAMOLECULAR SALT, AND A PHOTOGRAPHIC LIGHT-SENSITIVE ELEMENT FORMED FROM SAID EMULSION. THE PRESENT INVENTION ALSO EXTENDS TO THE DYES THEMSELVES AND A PROCESS FOR PREPARING THE SAME.

United States Patent O Im. 01. G03c N36 US. Cl. 96-101 16 ClaimsABSTRACT OF THE DISCLOSURE A direct positive silver halide emulsioncomprising at least one dye of the formula:

wherein Z 'is an organic substituted or unsubstituted atomic groupnecessary to complete a cycloheptatriene ring, which may be optionallysubstituted with a troponoid compound; Z is an oxygen atom or NH; Z isan 'or- 1 ganic substituted or unsubstituted atomic group necessary tocomplete a 5 or 6 membered heterocyclic ring; R is a member of the alkylseries selected from the group consisting of lower alkyl, hydroxy(lower) alkyl, lower 'alkoxy, sulfo (lower) 'alkoxy, vinyl methylaralkyl and sulfo :aralkyl; L and L are a group from the'methine series,said L capable of forming a methylene chain together with said -R; Xisan anion, and m and n each is 0 or 1, providing that n is 0 when the dyeforms an in-tramole'cular salt, and a photographic light-sensitiveelement formed I from said emulsion. The present invention alsoextendsto the dyes themselves and a process for preparing the same.

FIELD OF THE INVENTION The present invention relates to a silver halidephotographic emulsion and particularly to a direct positive photographicemulsion containing a novel dye.

DESCRIPTION OF THE PRIOR ART- When a silver halide light-sensitivematerial is exposed to light in a wave length region sensitive to thematerial and then developed, the image density is increased with anincrease in exposure, thus reaching a maximum value. When the exposureamount increases, the image density is reduced again and finally, areversal image is obtained. This phenomenon is generally termedsolarization.

'It has also been known that in some silver halide emulsions which arefogged optically or chemically, a similar reversal phenomenon by lightis observed. Hereinafter,

3,687,674 Patented Aug. 29, 1972 Thus, it is extremely important whenproducing direct positive light-sensitive materials to maintain adefinite or constant maximum density to, increase the sensitivity.

SUMMARY OF THE INVENTION It is, therefore, an object of the presentinvention to provide a direct positive silver halide photographicemulsion capable of maintaining a definite maximum density and providinga high sensitivity.

Accordingly, the object of this invention is attained by adding to thedirect positive silver halide photographic emulsion, a dye of theFormula I:

where-in Z represents an atomic group necessary to complete thecycloheptatriene ring. The group represented by Z may also besubstituted by a substituent known as a troponoid compound, such as, analkyl group having 1-4 carbon atoms, such as a methyl group, anisopropyl group, etc.; a halogen atom, such as a chlorine atom, abromine atom, etc.; an alkoxyl group such as a methoxyl group, etc.; anaryl group such as a naphthyl or phenyl group, a tolyl group and anitrophenyl group, etc.

Z represents 0 or NH.

Z represents an atomic group necessary to complete a S-membered or6-membered heterocyclic ring. Illustrative of the heterocyclic ringsrepresented by Z are those of the oxazoline series, oxazole series,benzoxazole, naphthoxazole series, thiazoline series, thiazole series,benzothiazole series, naphthothiazole series, selenazol series,benzoselenazole series, naphthoselenazole series, 2- pyridine series,4-pyridine series, 2-quinoline series, 4-quinoline series, imid-azoleseries, benzirnidazole series, naphthoimidazole series and the like.

The heterocyclic ring (which may comprise a heterocyclic ring per se ora benzene ring condensed with a heterocyclic ring) may be substituted byknown substituents in the field of sensitizing dyes such as an alkylgroup (C -C aryl group (phenyl or naphthyl), hydroxyl group, alkoxylgroup (C -C halogen atom (Cl, Br, F and I), and nitro group.

R represents a group of the alkyl series, such as a methyl group, ethylgroup, n-propyl group, B-hydroxyethyl group, B-rnethoxyethyl groupB-acetoxyethyl group, B-carboxyethyl group, 'y-sulfopropyl group,a-sulfobutyl group, vinylmethyl group, benzyl group, phenethyl group,p-sulfophenethyl group, etc.

L and L represents a group of the methine series, e.g., a methine groupor a methine group having a substituent such as a methoxyethyl group,ethoxyethyl, carboxyethyl and hydroxyethyl. In addition, L may form amethylene chain together with R.

X represents an anion such as halogen, perchlorate, ptoluene sulfonate,benzene sulfonate, thiocyanate, methyl sulfate, ethyl sulfate, etc., andm and n respectively, represent 0 or 1, providing that n is 0 when thedye forms intramolecular salt.

A general method for synthesizing the dye of the present invention isbriefly described below:

The dye represented by the above-mentioned general Formula I may beobtained by reacting a compound represented by the general Formula II:

CHO

. i 3 and a heterocyclic quaternary ammonium salt represented by thefollowing general Formula III:

R IETOH CH7;- OH: (X )n (In) in acetic anhydride under heating.

The definitions of Z, Z Z R, X, m and n in general Formulas II and IIIare the same as provided for general Formula I.

The compounds of general Formula II may be easily produced by oneskilled in the art based on the descrip tions in Daiyfiki Kagaku (GrandOrganic Chemistry), vol. 13, Non-Benzenic Aromatic Cyclic Compounds,published by Asakura Book Co.

The compounds of Formula III may be prepared according to thedescription given in the text Chemistry of Heterocyclic Compounds, vol.18 (1964).

The preferred embodiments illustrative of the dyes to be used in thepresent invention are those shown below. However, the dyes to be used inour invention are not limited to these exclusively.

Dye I O xMeOH I max. A 498 mp. T l: I

Dye 11.-.: 51 m Dye III--:: 495 mp:

Dye IV..;- 510 m CH=CN I C2H5 Dye V f E 510 111g.

OH=O H N-C H Dye VI. 532 my.

TABLEC0ntinued TABLE-Continued Dye XIV--.

CH3 CH3 A procedure for producing the dyes applicable to the presentinvention will be described below.

AMEO max.

586 mp: N O 9 Synthesis 1 (Dye I) 2-[2-(1-oxaazulane-2-one-3-yl)vinyl]-3-ethylbenzoxazolium iodide.To 1 ml.of acetic anhydride were added 30 mg. of 3-formyl-1-ozaazulanone and 60mg. of 3-ethyl-2-methylbenzoxazolium iodide. The mixture was heated to135 C. for 30 minutes on an oil bath. The crystals formed were collectedand washed with a large amount of hot ethanol, 40 mg. of a dark redcrystal having a melting point of 201 C. was obtained.

Synthesis 2 (Dye VII)2-[2-(l-azaazulan-Z-one-S-yl)vinyl]-3-ethylbenzothiazolium iodide.-To 3ml. of acetic anhydride were added 150 mg. of 3-formyl-1-azaazulanoneand 280 mg. of 3-ethyl-2-methylbenzothiazolium iodide. The mixture washeated to 135 C. for 30 minutes on an oil bath. When the crystals thusdeposited were washed with a large amount of hot methanol, 400 mg. of adark purple crystal having a melting point of 261 C. was obtained.

[It is astonishing that although the dye represented by the generalFormula I mentioned above shows no sensitizing effect (in other words,reduces the sensitivity in usual negative type photographic emulsions)it exhibits an excellent sensitizing effect to a direct positive silverhalide photographic emulsion.

The direct positive silver halide photographic emulsion containing thedye represented by Formula -I should exhibit a sensitivity which is highand maintain a maximum density of the photographic emulsion almostidentical to that of the photographic emulsion absent the dye.

In addition, the dye represented by Formula I to a direct positivephotographic emulsion, should maintain a low minimum density.

Usually, it is preferred to add the dye represented by Formula I to thesilver halide photographic emulsion as a solution. In this regard,suitable solvents for the dye solution may comprise Water, methanol andethanol.

The eifective amount of the dye to be added to the direct positivephotographic emulsion ranges from mg. to 1 g. and preferably, from 100mg. to 500 mg./kg. of emulsion.

The silver halide photographic emulsion to be used in the presentinvention may be fogged to the maximum density by light or the additionof a chemical fogging agent. If a chemical fogging agent is employed, itshould be one which fogs silver halide without impairing thephotographic emulsion. Illustrative of these are thiourea dioxide,stannous chloride, formaldehyde, or hydrazine.

Further, the silver halide emulsion to be used in this invention may befogged by addition of a combined chemical fogging agent and a gold salt.

Subsequent to the fogging operation of the silver halide emulsion,additional additives, such as a coating aid or a hardening agent may beincorporated in the photographic emulsion. Also, if desirable, a colorcoupler may be incorporated in the silver halide photographic emulsion.

The pH- and the pAg of the photographic emulsion are then adjusted andafter adding the dye represented by suitable support, there may beemployed, a syntheticresin film, such as a cellulose derivative film ora polyethylene terephthalate film, a glass sheet, a baryta-coated paper,a synthetic paper and a laminated paper.

A better understanding of the present invention will be attained fromthe following examples, which are merely illustrative and not limitativeof the present invention:

Example 1.Aqueous solutions of potassium bromide and silver nitrate wereadded simultaneously to an aqueous gelatin solution and the mixture wasstirred vigirously for 45 minutes at a temperature of 60 C., to formsilver bromide and after adding thiourea dioxide and potassiumchloroaurate, the mixture was warmed for 20 minutes. Thereafter, thesilver halide was sedimented by adding a sedimentation agent and afterdispersing the silver halide thus precipitated and washing it twice withwater, the silver halide was added and redispersed in an aqueous gelatinsolution containing 7.5% by weight of gelatin.

The emulsion was divided into several parts and after adding the dyerepresented by the general Formula I to each of the divided emulsions,the emulsion was applied to a cellulose acetate base and then dried.

The sample thus produced was exposed by means of a sensitometer anddeveloped for 2 minutes at 20 C., using a developing liquid having thecomposition shown in Table 1.

TABLE 1 G. Metol 3.1 Hydroquinone 12 Sodium sulfite 45 Anhydrous sodiumcarbondate 67.5 Potassium bromide 1.9

Water to make 1 liter.

TABLE 2 Amount of dye (mg./kg.- Relative Dmax. when Dmiu. when emulsion)sensitivity not exposed exposed None (control) 12. 9 1. 59 1.46 Dye VI(400) 445 1. 48 0. 31 Dye VIII (400) 214 1. 51 0.62 Dye XI (400) 99 1.41 0.60 Dye XII (400) 301 1. 52 0. 73

1 Pinacryptol yellow.

Example 2.An aqueous solution of potassium bromide and silver nitratewere added simultaneously to an aqueous gelatin solution. The mixturewas stirred for 45 minutes at 60 C., to form silver bromide. Then,potassium iodide (0.6 mole percent of silver nitrate) was added to theemulsion and the emulsion was ripened for 40 minutes.

After the ripening was completed, hydrazine dihydrochloride andpotassium chloroaurate were added to the emulsion, the mixture beingwarmed for 16 minutes at 45 C. Subsequently, the silver halide wasprecipitated by adding a floculating agent thereto. The silver halidethus precipitated was recovered, washed twice with water and thendispersed in an aqueous gelatin solution containing 7.5 by weight ofgelatin.

The silver halide photographic emulsion thus prepared was divided intoseveral parts. After adding the dye represented by Formula I to each ofthe divided photographic emulsions, the mixture was stirred and thesilver halide emulsion was applied to a cellulose acetate film anddried. The sample thus dried, was exposed by means of a sensitometer anddeveloped for 2 minutes at 20 C.,

using a developing liquid having the composition shown in Table 1 anddescribed in Example 1. Then, the sample was fixed, washed with waterand dried. After processing, by measuring the optical density of thesample by means of a densitometer, the characteristic curve wasobtained. The results thus obtained are shown in Table 3.

TABLE 3 Furthermore, almost the same results were obtained by repeatingthe same procedure using Dyes (III), (VII), (IX) and (X) shown above.

Example 3.An aqueous solution containing 70 gms. of potassium bromideand 6 gms. of sodium chloride as well as an aqueous solution containing100 gms. of silver nitrate were added simultaneously to an aqueousgelatin solution containing 10% by weight of gelatin. The mixture wasreacted at a temperature of 50 C., to form a fine grained silver halide.Then, after adding 1 gm. of potassium iodide and 40 grns. of gelatinthereto, the mixture was adjusted to a pH of 9.5 with sodium carbonate.Thereafter, to said emulsion was added ml. of an aqueous solutioncontaining 1% by weight of hydrazine dihydrochloride. The emulsion wasripened for 40 minutes to form fog-nuclei. Then, the emulsion wasadjusted to a pH of 6.0 by the addition of (by weight) of citric acid,cooled and washed with water.

The silver halide photographic emulsion thus produced was divided intoseveral parts. After adding the dye represented by Formula I to each ofthe divided photographic emulsions and stirring the mixture, the silverhalide emulsion was applied to a cellulose acetate and dried. The samplethus dried was exposed by means of a densitometer and developed for 2minutes at 20 C., using developing liquid having the composition-shownin the Table 1 and described in Example 1. Then, the sample was fixed,washed with Water and dried. After processing, by measuring the opticaldensity of the sample with a densitometer, the characteristic curve wasobtained.

The results thus obtained are shown in Table 4.

Dyes XIII and XIV exhibit the same properties as shown above for thosedyes already enumerated.

Though the present invention has been adequately described in theforegoing specification and examples included therein, it is readilyapparent that various changes and modifications may be made withoutdeparting from the scope thereof.

8 What is claimed is: 1. A direct positive silver halide photographicemulsion comprising fogged silver halide grains and at least one dye ofthe formula:

wherein Z is a troponoid substituent on the cycloheptatriene ring saidsubstituent is a member selected from the group consisting of loweralkyl (C -C halogen, lower alkoxyl, aryl, alkylaryl and nitroaryl; Z isan oxygen atom or N--H; Z is an organic substituted or unsubstitutedatomic group necessary to complete a 5 or 6 membered heterocyclic ringselected from the group consisting of the thiazole series,naphtholthiazole series, selenazole series, benzolselenazole series,naphoselenazole series, 2-pyridine series, 4-pyridine series,Z-quinoline series, 4-quinoline series, imidazole series, benzimidazoleseries and naphthoimidazole series; R is a member of the alkyl seriesselected from the group consisting of lower alkyl, hydroxy (lower)alkyl, lower alkoxy, sulfo (lower) alkoxy, vinylmethyl, aralkyl andsulfo aralkyl; L and L are a group from the methine series, said Lcapable of forming a methylene chain together with said R; X is an anionand mand n each is O or 1, providing that n is 0 when the dye forms anintramolecular salt, said dye being present in a sensitizing amount.

2.-The emulsion of claim 1, wherein said dye is a member selected fromthe group consisting of:

'L/ of til) 021140 CH3 S O CzHs NW 3. The emulsion of claim 1, whereinsaid silver halide photographic emulsion is fogged to the maximumdensity by light.

4. The emulsion of claim 1, wherein said silver halide photographicemulsion is fogged to the maximum density by the addition of a chemicalfogging agent.

5. The emulsion of claim 4, wherein said chemical fogging agent is amember selected from the group consisting of thiourea dioxide, stannouschloride, formaldehyde and hydrazine.

6. The emulsion of claim 1, wherein said silver halide photographicemulsion is tagged by the addition of a combination of a chemicalfogging agent and a gold salt.

7. An emulsion as claimed in claim 1, wherein an amount of the dye to beadded to the emulsion ranges from 10 mg. to 1 gm./kg. of emulsion.

8. A photographic light-sensitive element comprising a support havingthereon at least one layer containing the direct positive silver halidephotographic emulsion of claim 1.

9. The emulsion of claim 1, wherein the lower alkyl (C -C troponoidsubstituent is a member selected from the group consisting of methyl andisopropyl.

10. The emulsion of claim 1, wherein the halogen troponoid substituentis a member selected from the group consisting of chlorine and bromine.

11. The emulsion of claim 1, wherein the lower alkoxyl troponoidsubstituent is methoxyl.

12. The emulsion of claim 1, wherein the aryl troponoid substituent is amember selected from the group consisting of naphthyl and phenyl.

13. The emulsion of claim 1, wherein the alkyl-aryl troponoidsubstituent is tolyl.

14. The emulsion of claim 1, wherein the nitro aryl troponoidsubstituent is nitro phenyl.

15. The emulsion of claim 1, wherein L and L are members selected fromthe group consisting of methine, methoxyethyl methine, ethoxyethylmethine, carboxyethyl methine and hydroxyethyl methine.

16. The emulsion of claim 7, wherein the amount of dye to be added tothe emulsion ranges from mg.- 500 mg./ kg. of emulsion.

References Cited Ishikawa et al.: Seven Membered Ring Compounds as aDesensitizing Agent, Bulletin of the Society of Scientific Photographyof Japan, No. 18, December 1968, pp. 5-15.

NORMAN G. TORCHIN, Primary Examiner W. H. LOUIE, 111., AssistantExaminer US. Cl. X.R. 260-240

